Releasable suspension device for supporting conductors from masts



Sept. 22, 1964 3,150,229

- G. Z. MILOW RELEASABLE SUSPENSION DEVICE FOR SUPPORTING CONDUCTORS FROM MASTS Filed March 29, 1962 lnvenlor GAR RY ZVI MlLOW By n -1w M Kim A tlofneyl up the jerk in case of breakage of the line.

United States Patent 3,150,229 RELEASABLE SUSPENSION DEVICE FOR SUP- PORTING CONDUCTORSFROM MASTS Garry Zvi Milow, 23 Hagilgal St., Ramath Gan, Israel Filed Mar. 29, 1962, Ser. N 183,574 3 Claims. ((11. 17 445) The present invention relates to overhead power lines and more particularly to a device for suspending the conductors of such lines from the horizontally extending arms of intermediate upright masts or poles. As is known, the conductors, being metal cables, are of considerable weight and thus the masts have to carry a heavy load. Such load is the result of several components:

(a) The weight of the. conductors, insulators, hardware and possibly snowand ice-loads, acting as vertical forces,

(b) Horizontal or transversal forces due to wind pressure on conductors,

(0) Longitudinal forces producing torsion and bending, acting on the towers and poles if a conductor is broken.

Under normal conditions the result of said components is directed vertically downwards. Every section of cable exerts also a pull in a longitudinal direction, i.e.

in the direction away from its point of suspension. But

the pull exerted by one section of a conductor is eliminated by the pull of the subsequent section which acts on the same point of suspension, but in opposite direc- .tion. This equilibrium is upset when the cable is torn or breaks in one of its sections. Then this torn section ceases .to exert pull onto the point of suspension of the conductor, the consequence being that the pull by the next following section is so strong that it tends to tilt or overturn the mast and also to twist it. Thus, the designer has .to reckon with such a contingency and has to dimension the foundations of a mast and its parts accordingly. In other words, a mast or pole could be dimensioned much more economically if the designer would not be compelled .to take into account the one sided stresses exerted by a section of cable when these are not compensated for by the next following section.

Attempts have been madeto eliminate the foregoing drawbacks by using special conductor clamps which would provide for an elastic intermediary member interposed between the mast and the conductor for taking Such a construction is described in French Patent No. 999,229, which comprises a cable wound on a drum and carrying the insulator string and thereby the conductor, the cable becoming unwound under certain circumstances, thus freeing the mast from the extreme stress.

Another construction provides for a detachable connection between .the lower end of the insulator string and the conductor clamp. For the actual separation in case of breakage it relies on the inertia of the heavy string of insulators which will not immediately follow the movement of the clamp (see German Patent No. 446,119).

The first named arrangement is rather complicated and it is doubtful whether it will function, i.e. the cable will unwind in an emergency which might occur years after installation. The second solution is not reliable for the reason mentioned above.

It is clear that the connection-when becoming only slightly stuckwill overcome the inertia of the string and no separation will occur.

The present invention offers a solution which, at least in part, solves the problem refer-red to above and allows the mast or pole to be dimensioned much more economically than hitherto.

Thus, it is the object of the invention to provide a suspension device for overhead power lines which will I there is provided on the bolt 8 a washer 9'.

automatically disrupt the connection between the elec trical conductor and the respective mast or tower, whenever the conductor breaks. sudden jerk acting on the mast is obviated, as well as torsion-a1 forces .tending to turn the mast about a vertical axis.

According to the invention, there is provided a suspension device for supporting a conductor from a mast and for protecting the mast against excessive longitudinal forces in event of breakage of the conductor, the suspension device comprising two hingedly connected parts; means for connecting one part to the mast; and means for connecting the other part to the conductor. One of the parts includes a head having a convex surface at one side thereof and a knife edge on another side thereof; the other part being formed with a concave surface engageable by the convex surface, and further with an indentation in which the knife edge is received. The convex surface has a radius of curvature greater than the height of the one part between the knife edge and the convex surface, whereby the convex surface of the head slides on the concave surface, and the knife edge becomes unseated from the indentation, when a predetermined angle between the two parts is exceeded caused by an excessive longitudinal force corresponding to that occurring upon breakage of the conductor.

The suspension device is particularly for use in overhead power lines having a mast, wherein the mast includes a string of insulators connected between the conductor-carrying part of the suspension device and the conductor. Flexible supporting means are provided (such as a cable) loosely connected at one end to the mast and at the other end to the conductor-carrying part of the suspension device at a point above the insulator string. As disclosed, the suspension device is hinged to the mast permitting its parts to move as a whole from the vertical in a direction perpendicular to the conductor.

These and other features will become clear from the following detailed description in connection with the drawings, showing in FIGURE 1 a fractional perspective view the suspension of a conductor from a mast, using the new suspension means.

FIGURE 2 is a side elevation, partly in section, of the new suspension means, and FIGURE 3 is a side elevation turned through against that of FIGURE 2 and seen in the direction of the power line.

From a mast I extend horizontal arms, only one of which, 2, is shown in FIGURE 1. From the end of that arm 2 is suspended, by means of the new device as Will be described, a string of insulators 3 of known de sign, from the lowermost of which is suspended in a known manner a through-going, substantially horizontal conductor 4.

Referring now to FIGURES 2 and 3, the new device comprises, in the example shown, a rectangular plate 5 having an integral, downwardly extending lug 6 at its middle. To lug 6 is hinged by means of two eyes 7 and a headed bolt 8, secured by a cotter 9, the above briefly described slotted member 11. Below cotter 9 Plate 5 is intended to be fixed to the underside of arm 2 at its other end by screws 19. Member 11 has a throughgoing horizontal channel 12, merging at its lower side into a straight slot 13 extending in parallel to channel 12 and open at both ends. Channel 12 is wider than slot 13, so that at the bottom of the former two parallel shoulders 14 are forme'. These shoulders (see FIG- URE 2) are slightly concave in longitudinal direction for a purpose to be set out. The upper side of channel 12, i.e. its roof, has at its middle a crosswise extend- By this disengagement the ing indentation or groove 15. At both sides therefrom it is shaped into a wavy or irregular surface. Within channel 12 there is accommodated the head portion 16 of a substantially rod-like member 17. Portion 16 extends at two opposite sides from rod 17 and has a rounded underside 18 and a. knife-like top edge 19, and rests with that underside on the curved faces of the shoulders 14. Member 17 is thus suspended from member 11, extending downwards through slot 13 which it fits loosely. The lower portion of member 17 is of a restricted diameter forming a cylindrical portion 17 and ends in a thickened bulbous portion 17". The central portion of member 17, which is of rectangular cross section, is provided with two superposed cross bores 20, 2-1. To portion 17 will be fixed an insulator (or the uppermost of a string of insulators 3) in a known manner. In cross bore 20 is fixed one end of a strong wire or cable 22 (see FIGURE 1) the other end of which is fixed to arm 2 at 23, as near to mast 1 as actually feasible. Cable 22 hangs loosely between its two fixed ends. Cross bore 21 serves for fixing th rein arcing horns or rings as known per se.

If a conductor 4 is suspended at an intermediary point as shown in FIGURE 1, the load on arm 2 will act substantially vertically downwards because of the weight. The forces of mechanical tension, acting in the direction of arrows a and b will act again-st, and nullify each other. The bending moment exerted on the mast 1 through arm 2 will be equalized by a similar moment at the left hand end (not shown) of the said arm. This equilibrium, however, will be disturbed whenever a cable breaks. In such a case the pull exerted on the suspension means in the direction of the break will cease suddenly, leaving them to the one-sided pull of the still intact portion of the cable. sum of the weight of the cable plus the mechanical tension in longitudinal direction imparted to the cable when being mounted. It will pull the string 3 of insulators and also the rod-like member 17 sideways, say in the direction of arrow y in FIGURE 2. Head 16 will thereby slide on shoulders 14, the knife edge 19 will become detached from groove 15, and the head 16 will be pulled out of channel 12 with the said knife edge sliding on the wavy roof of channel 12, and the member 17 will fall down, relieving the tension in the cable and relieving the end of arm 2 of the load and thus of the stress.

It would, however, be undesirable, to let in this way afurther portion of the cable (in addition to the broken one) fall to the ground together with the string of insulators. For this reason the wire or cable 22 is provided. As it is flexible and as its connection with arm 2 is much nearer to the vertical axis of the mast 1, and also as it effectively lengthens the broken conductor, the torsional or longitudinal force exerted on the mast is greatly reduced or eliminated. The presence of wire or cable 22 and the fact that this latter holds the broken conductor suspended, of course, facilitates repair works. By being able to ignore the torsion and bending forces acting on the tower or poles, the designer, in his calculations, can take smaller maximal loads into account than otherwise.

- Of course, small differences of magnitude in the forces a and b which may occur either during mounting or later, will not lead to the above-described disengagement of part 17 from part 11, but simply to a slight deviation of rod 17 from the vertical to the left (arrow x) or to the right (arrow y) as the case may be.

The functioning of the device has been described assuming a substantially horizontal course of the power line. In mountainous country, however, it frequently happens that the cable portion at one side of the mast This pulling force is the will hang much deeper than the subsequent cable-portion at its other side and, consequently, the two angles alpha, beta (see FIGURE 1) will become unequal. So that rod 17, in case of a break, may slip out of its channel 12 smoothly, member 11 will have to be shaped asymmetrically, i.e. elongated at one side and/ or possibly shortened at the other side. A very few standard forms for the bodies 11 will be sufiicient for all practical cases. The radius of curvature of the shoulders 14 must, in all cases, be greater than the height of .the head 16 because otherwise it would be clamped in channel 12 while being turned about its knife edge 19.

Part 11 together with part 17 are swingable about pin 8 in a direction perpendicular to that of part 17 within channel 12, i.e. perpendicular to the direction of the. cable 4. Thus, if the mast 1 is placed at a corner point of the power line, the suspension means can yield to the lateral pull and assume together an inclined position, the relative position of parts 11 and 17 remaining unchanged.

So that, during transport and/or erection, the parts 11 and 17 should not be separated, a set screw 31, to be later removed, may be provided, fixing the said two parts temporarily to each other.

What I claim is:

1. A suspension device for supporting a conductor from a mast and for protecting the mast against excessive longitudinal forces in event of breakage of the conductor, comprising: two hingedly connected parts; means for connecting one part to the mast; means for connecting the other part to the conductor; one of said parts including a head having a convex surface at one side thereof and a knife edge on another side thereof; the other of said parts being formed with a concave surface engageable by the convex surface of said one part, and with an indentation in which said knife edge of said one part is received, said concave surface having a radius of curvature greater than the height of said one part between said knife edge and said convex surface, whereby said convex surface of said head slides on said concave surface, and said knife edge becomes unseated from said indentation, when a predetermined angle between the two parts is exceeded caused by an excessive longitudinal force corresponding to that occcurring upon breakage of the conductor.

2. In an overhead power line having a mast and a conductor supported in suspension therefrom, the combination comprising: a suspension device as defined in claim 1; a string of insulators connected between the conductor-carrying part of the suspension device and the conductor; and flexible supporting means loosely connected at one end to the mast and at the other end to the conductor-carrying part of the suspension device at a point above said insulator string.

3. The combination as defined in claim 2, wherein the suspension device is hinged to the mast permitting its parts to move as a whole from the vertical in a direction perpendicular to the conductor.

References Cited in the file of this patent UNITED STATES PATENTS 1,841,656 Woodruff et al. Jan. 19,1932 1,939,964 Fleming Dec. 19, 1933 3,005,866 Fraser Oct. 24, 1961 FOREIGN PATENTS 437,118. Germany Nov. 15, 1926 492,259 Germany Feb. 19, 1930 603,148 Germany Sept. 24, 1934 348,478 Great Britain May 14, 1931 405,732 Italy Sept. 4, 1943 166,151 Austria June 26, 1950 

1. A SUSPENSION DEVICE FOR SUPPORTING A CONDUCTOR FROM A MAST AND FOR PROTECTING THE MAST AGAINST EXCESSIVE LONGITUDINAL FORCES IN EVENT OF BREAKAGE OF THE CONDUCTOR, COMPRISING: TWO HINGEDLY CONNECTED PARTS; MEANS FOR CONNECTING ONE PART TO THE MAST; MEANS FOR CONNECTING THE OTHER PART TO THE CONDUCTOR; ONE OF SAID PARTS INCLUDING A HEAD HAVING A CONVEX SURFACE AT ONE SIDE THEREOF AND A KNIFE EDGE ON ANOTHER SIDE THEREOF; THE OTHER OF SAID PARTS BEING FORMED WITH A CONCAVE SURFACE ENGAGEABLE BY THE CONVEX SURFACE OF SAID ONE PART, AND WITH AN INDENTATION IN WHICH SAID KNIFE EDGE OF SAID ONE PART IS RECEIVED, SAID CONCAVE SURFACE HAVING A RADIUS OF CURVATURE GREATER THANT THE HEIGHT OF SAID ONE PART BETWEEN SAID KNIFE EDGE AND SAID CONVEX SURFACE, WHEREBY SAID CONVEX SURFACE OF SAID HEAD SLIDES ON SAID CONCAVE SURFACE, AND SAID KNIFE EDGE BECOMES UNSEATED FROM SAID INDENTATION, WHEN A PREDETERMINED ANGLE BETWEEN THE TWO PARTS IS EXCEEDED CAUSED BY AN EXCESSIVE LONGITUDINAL FORCE CORRESPONDING TO THAT OCCURRING UPON BREAKAGE OF THE CONDUCTOR. 